1. Field of the Invention
The present invention relates to a speaker, and more particularly to a speaker in a slender structure having a diaphragm of narrow width.
2. Related Art of the Invention
The speaker is generally round in shape, but speakers in a slender structure are also widely used, for example, in television applications. The speakers for television are generally installed at both flanks of a cathode-ray tube. In this case, in order to minimize the lateral width of the television, speakers in a slender structure are preferably used.
In the conventional speakers in a slender structure, generally, since the slender diaphragm is driven, torsional resonance in the direction of major axis is likely to be excited if there is any unevenness in the driving force, dimension, weight, etc. As a result, in the mid- or high-range band, peak dip occurs in the reproduced sound pressure frequency characteristic, and it may possibly lead to increase of distortion or deterioration of sound quality.
In the conventional circular speaker, a viscoelastic material was sometimes applied on the entire circumference of the edge adhered to the outer circumference of the diaphragm for suppressing the resonance of the diaphragm. In resonance, the diaphragm vibrates concentrically. Accordingly, the outer circumference of the diaphragm vibrates alike on the whole circumference. As the entire edge circumference is coated with the viscoelastic material, the resistance component can be given to the entire diaphragm, and vibration due to resonance can be braked. However, in the case of torsional resonance which is likely to occur in a speaker in a slender structure, the diaphragm does not vibrate concentrically with the edge. Hence, the vibration amplitude differs from one part to other at the edge coated with the viscoelastic material over the entire circumference of the edge, and the resistance components cannot be given effectively, and there was a problem of increase of weight.